PROJECT SUMMARY Sleep duration and quality is worse among racial/ethnic minority groups, particularly African Americans/blacks and Hispanic/Latinos. Impaired sleep has been associated with detriments in cognitive function, which is a major cause of poor quality of life and disability among older adults. Impaired cognitive function and Alzheimer?s Disease are also more often observed in racial/ethnic minority groups, including blacks and Hispanic/Latinos, leading to greater disparities in well-being and longevity among these groups. Given the importance of maintaining cognitive function at older ages, we propose to examine sleep disparities among a cohort of 450 older adults (?65 years) from three racial/ethnic groups to understand better the correlates of these sleep disparities and to understand the role sleep plays in disparities in cognitive function and Alzheimer?s disease risk. Defining the correlates of inadequate sleep and the contribution of sleep to cognitive function in a racial/ethnically diverse sample is the first step towards identifying modifiable factors within each racial/ethnic group contributing to sleep and cognitive function. Inadequate sleep has been associated with adverse cardiovascular function, including higher blood pressure and elevated ratio of white matter hyperintensities to normal tissue in the parietal region of the brain. Inadequate sleep has also been associated with increased insulin resistance and diabetes risk in experimental and observational studies. Cerebral small vessel disease and insulin resistance are risk factors for the development of impaired cognitive function and Alzheimer?s disease and thus we will examine whether these measures mediate associations between sleep and cognitive function. We will enroll 150 non-Hispanic blacks, 150 non-Hispanic whites and 150 Hispanic/Latinos without severe cognitive impairment. We will assess habitual sleep, cognitive function, insulin resistance and cerebral small vessel function at baseline and 24 months later. We will determine the contribution of psychosocial and physical well-being to sleep disparities in older adults. We will also determine whether inadequate sleep partially mediates racial/ethnic differences in cognitive function decline over 2 years. Finally, we will test whether cerebral small vessel disease and insulin resistance are potential mechanisms linking inadequate sleep to declines in cognitive function in older adults. This application aligns with the goals of the NIH Sleep Disorders Research Plan to ?Identify ? lifestyle factors ? contributing to the risk of sleep and circadian disorders and disturbances, and their role in the development and pathogenesis of co-morbid diseases, and disability.? If inadequate sleep is a significant correlate of greater cognitive decline among older adults, the development of novel therapies, behavioral interventions and/or methods to increase use and adherence to existing therapies to improve sleep in older adults, particularly ones tailored to the specific needs of racial/ethnic minorities, could have a significant impact on public health and help to eliminate disparities.